1. Field of the Invention
The present invention relates to a method used in a wireless communication system and related communication device, and more particularly, to a method of handling a beamforming feedback in a wireless communication system and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system supporting the 3rd Generation Partnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standard are developed by the 3GPP as a successor of a universal mobile telecommunications system (UMTS), for further enhancing performance of the UMTS to satisfy increasing needs of users. The LTE system includes a new radio interface and a new radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicating with multiple user equipments (UEs), and communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control.
A LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint (CoMP) transmission/reception, UL multiple-input multiple-output (MIMO), etc. For a UE and an eNB to communicate with each other in the LTE-A system, the UE and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions.
In addition, it is expected that a beamforming (e.g., 3D-beamforming) realized at the eNB can be further improved to enhance throughput of the eNB. For example, the UE can feedback channel information which is accurate enough to the eNB, such that the eNB can realize the beamforming with a high accuracy according to the channel information. However, a large amount of overhead is needed for feeding back the channel information with a high accuracy or a high precision. Not only power consumption of the UE is increased, but throughput of the UE is decreased.
Thus, feeding back the channel information efficiently is important problem to be solved, to realize the beamforming in practice.